Ecological Impacts of Wind Farms:

Global Studies

Are Wind Farms Hazardous to Birds and Bats? Stephen J. Ambrose

Impact Phases

Construction Phase:

Habitat clearance

Disturbances (noise, visual, dust etc.)

Operational Phase

Direct mortality (birds & bats)

Changes in food abundance

(e.g. aerial insects)

Construction Impacts:

The UK Experience (Birds)

Degree of disturbance depends on:

Number of turbines.

Bird species present at the site.

Seasonal patterns of habitat use.

Availability of alternative habitat.

Construction Impacts:

The UK Experience (Birds)

Extent of disturbance around wind

farm varies according to species:

Grassland songbirds: 80 m

Waterfowl: 800 m

Seabirds: 4 km (4000 m)

Zone of disturbance often reported:

600 m

Construction Impacts:

The UK Experience (Birds)

The nature & magnitude of construction impacts depend on sensitivity of species to disturbances and their resilience to habitat modification.

Decrease in population densities of timid species in wind farm areas due to disturbances (Red Grouse, Snipe & Curlew)

Increase in population densities of species which favour open swards (expanses of short grass) (Skylarks, Meadow Pipits & Stonechats)

Decrease in population densities of species which favour tall grasses and/or shrubs (Wheatear)

No significant impacts on other species studied (Golden Plover, Lapwing, Dunlin)

Greater impacts of UK wind farms on bird populations during

construction than subsequent operation

Journal of Applied Ecology

Volume 49, Issue 2, pages 386-394 13 MAR 2012 DOI: 10.1111/j.1365-2664.2012.02110.x

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2664.2012.02110.x/full#f1

Operational Impacts: Direct Mortality

Wind turbines can kill birds and bats.

Bird groups most at risk in Northern Hemisphere:

Migrating songbirds (~ 75% of mortalities at

US wind facilities).

Raptors (esp. on migration & in foraging areas).

Migrating waterfowl (turbines near wetlands).

Migrating shorebirds (marine & shoreline

turbines).

Mortality varies widely across regions and wind

resource areas.

Flocking Bramblings in Berne, Switzerland

about to start autumn migration

Raptors on migration in Cadiz, Spain

Start of autumn shorebird

migration in Alaska.

Why do Birds Collide with

Wind Turbines?

Location of wind farms along major

migratory routes (strong wind

areas).

Inclement weather (e.g. heavy fog)

Nocturnal migration.

Bird abundance, e.g. more raptor

fatalities as raptor abundance near

turbines increases.

Why do Birds Collide with

Wind Turbines?

Some species that forage close to

turbines (e.g. Red-tailed Hawks,

Golden Eagles) more susceptible

to collisions.

Other aerial soarers (e.g. corvids)

appear to avoid collisions with

turbines.

Bat Mortality at Northern

Hemisphere Wind Farms

North-western Europe (bats/turbine/year):

Flat, open inland farmland: 0 - 3

In more complex agricultural farmland: 2 - 5

On coast & forested hills & ridges: 5 – 20.

Germany

~ 200,000 bats/year, depressing bat populations up to 3,300 km away.

Spain: 200-670 bats/turbine/year

United States: 0 to 40 bats/MW/year

Possible Causes of Bat Mortality

at Wind Turbines

Proximate Causes (causes of death)

Collisions with towers & rotating

blades.

Barotrauma?

Lung Damage in Bats

(Barotrauma?)

Possible Causes of Bat Mortality

at Wind Turbines

Ultimate Causes (why bats collide with turbines)

Random Collisions (i.e. due to chance).

Coincidental collisions (spatial, temporal & demographic variation).

Weather-dependent: most fatalities occur on nights with low wind speed & typically before & after the passage of storm fronts.

Bats are attracted to turbines (tree roosting spp. & foragers of aerial insects).

King Island Bats

Lesser Long-eared Bat

(Nyctophilus geoffroyi)

Gould’s Wattled Bat

(Chalinolobus gouldii)

Mitigation Measures

1. Pre-development site evaluation (EIA):

Will there be impacts to birds and bats at levels of concern?

What sites should be avoided?

How can the wind farm be designed & operated to lessen impacts?

2. Locate wind farms in flat, open agricultural landscapes rather than near important bird & bat habitats

Mitigation Measures

3. Curtailment:

Increase “cut-in speed” of turbines during low-wind periods (when bats are most active).

4. Feathering:

Swivelling rotor blades on a bearing to decrease angle of wind attack and hence their lift.

5. Use of radar to detect large bird migrations near wind farms.

Turbine in “Feathered Condition”

at a Canadian Wind Farm

Example of a portable radar station

Use of Radar to Detect Mass

Bird Migration

Mitigation Measures

6. Shorter turbine heights?

Shorter turbines & narrower, shorter blades

= smaller sweep areas

= smaller blade-tip vortices and

= less blade-wake turbulence.

7. Making turbines more “visible”:

Ultraviolet paint

Flashing red lights

Mitigation Measures

8. Purple wind turbines attract

significantly fewer insects than white

or light grey ones.

9. Does wildlife become habituated to

wind farms? Need for further study.